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Objective: Phylum Platyhelminthes, Nematoda.
Body PlanBilateral Symmetry
- Mirror image (left side mirrors right side)
Body Plan
3 Tissue Layers:
Ectoderm: body covering
Mesoderm: internal tissue (muscle)Endoderm: - Gastrovascular cavity or digestive tract
Body Cavities- Coelom- body cavity that holds organs• Acoelomate: animal that lacks a fluid filled
body cavity
Digestion
- Gastrovascular cavity: food enters and exits through this muscular sac
Major CharacteristicsMovement: - Ventral cilia- Muscles
Eyespots: detect lightNervous system: anterior clusters of nerve
cells, side flaps for sense of smell
Class Turbellaria
Example: Planarians (marine, freshwater), free-living
Class Trematoda
Example- Blood fluke, parasites
http://www.youtube.com/watch?v=uWvHvl25oXI
Class Cestoidea
Description- Parasitic
• No digestive or circulatory system• Absorb nutrients
Ex: Tapeworm!
http://animal.discovery.com/videos/monsters-inside-me-meter-long-tapeworm.html
Phylum Nematoda (Roundworms)
• Have bilateral symmetry and 3 tissue layers like flatworms
• Different from flatworms because they have:
• Complete Digestive Tract: - Opposite mouth and anus
- Digestive tube
Body Plan
Pseudocoelm:- fluid filled body cavity in direct contact with the digestive tract, worm thrashes to distribute nutrients
Diversity
• Most are free-living and decomposers
• Some are Parasites• Ex: Heartworm
http://animal.discovery.com/videos/monsters-inside-me-flesh-eating-hookworm.html
http://animal.discovery.com/videos/monsters-inside-me-lymphatic-filariasis.html
Phylum Annelida (Annelids) aka Segmented Worms
Body Plan
- Divided into sections by internal walls-
- Digestive tract, nerve cord, and main blood vessels not segmented
• Have bilateral symmetry and 3 tissue layers
Closed Circulatory System:
• Blood remains in vessels
- nutrients, oxygen, and wastes diffuse
Coelm
• True, fluid filled body cavity in contact with internal tissues
Anatomy• Pharynx: beginning of
digestive tract• Crop: stores food
temporarily• Gizzard: soil mixture is
ground up• Clitellum: flat area near
anterior end• Responsible for secreting
mucus for mating and creating cocoons for offspring
• Setae: tiny hairs on ventral side for movement
Class Polychaeta
Class Oligochaeta
• Example: Earthworms
Class Hirudinea
• Example: Leeches